D7H hot trans
D7h 79Z 1753
Any ideas on whats up on this?
Trans wants to run hot. With the radiator real clean can keep the motor temp down to 190. The trans doesn't shoot off the fault light when it gets to 230+, but it seems to pull up the hyd temp that does trigger the fault light at about there.
Have pulled the trans and motor oil cooler, there was some blockage (silicone) and cleaned.
Trans lube pressure was 10 psi low and replaced trans pump with cat rebuilt.
Changed hyd and trans filters and checked screens.
The trans is the first thing to heat up (hour to mid way and just keeps going up) and pulls the motor and hyd up it seems. Even at a fast idle not moving the trans will never cool to the same temp as the motor. The hyd is slow to heat up, but after 3 hrs or so of steady running climps up to the trans temp.
I don't think the tractor has a hyd cooler, it does have a third valve.
Pushing is 1st gear building pond dam, easy backup in 2nd.
It has been +100 degree weather.
There was a cat reman of trans not quite 2000 hrs ago before i bought the tractor.
Know that was done, was told torque was done but haven't got proof.
Have checked temps with thermal gun.
Couple thoughts for you....
I would check the oil pressure drop across the trans oil cooler and the delta T across it. You mentioned cleaning the cooler, but it may be worth your while to test it anyways. Cat provides a small pipe plug test port on each side of the cooler for this purpose. Could the trans or torque converter be slipping a bit and making some extra heat? I would do a stall test and rule that out. What viscosity of oil do you have the trans filled with?
With those high ambient temps you are dealing with, it's a good idea to make sure the engine cooling system is in perfect shape. Make sure the fan shroud is intact, drive belts and sheeves in good shape, engine enclosure guards are installed and the cooling system is pressurized to spec because the engine has to dump the trans heat as well at it's own generated heat. For good measure, check the delta T across the inlet of the engine jacket water pump to inlet of the water regulator housing. You should be seeing a 12 to 15 F delta. If it's more than that, it's a flow problem. If the delta T is less than that, it's a capacity problem.
Most of the time, these overheat issues are an accumulation of a bunch of little issues all combined with the above normal temps you guys down south are dealing with this summer. Good luck
The torque will heat up quickly at full stall. I tried it and if I remember right it went from 200 to 230 in about 20 seconds.
Is there a correct way to do a field test of the torque converter?
Will check the engine delta tomorrow. And will try and get the pressure check on the cooler.
Would not be surprised if it is the torque converter, appreciate the help figuring out for sure rather than me throwing (more) parts at it.
Universal brand 21C T0-4 Trans Oil 30W
It sounds like the engine is cooling like it should. 190* in the heat we have this year is good. The trans temp usually runs 20-30 degrees warmer. If ther is some problems, a thourough pressure test of the trans and torque will reveal the problem.
If your machine has a hyd cooler, it will be on the mounted to the radiator, between the engine and the fan. Your machine doesn't have Differential steering, correct? If there isn't a cooler or diff steer, I doubt the hyd and trans overheat problem are related. It sounds to me like you have a lack of oil flow through the transmission oil cooler. When you are stalling it and get the oil temp from 200 to 230 in 20 seconds, how fast does it cool back down when you put it in neutral? how about 230 to 260? (the alarm should sound @ 260) You mention you had low lube pres., did the new pump fix it? Lube pressure is directly related to cooler flow. No cooler flow=low lube pres. Low cooler flow is often caused by a worn out torque conv. When the converter wears out, it leaks oil, not on the ground, but into the torque converter housing, where the scavenge pump picks it up and returns it to the sump. When this happens the oil doesn't go through the cooler, and the whole transmission gets very hot after a while. This is why the engine coolant temp gauge stays cool. The transmission's heat never makes it to the radiator. Another sometimes overlooked problem on high drive dozers is a leak in an Internal transmission tube. These machines have a bunch of formed metal tubes running inside the trans/steering clutch housing, and an internally leaking tube can cause alot of problems, and be very hard to find. Anyways, I might focus on oil cooler flow if it were me. Bear in mind, if the problem is cooler low flow, it will only be low when the machine is hot (as in the gauge wont come down, running hard 3-4 hours hot. Good luck, keep us posted. Hopefully American Independant will chime in, he always has some good ideas.
Ok checked the following transmission pressure taps and first three were within specifications;
L pump pressure 465 psi
A converter inlet 90 psi
E converter outlet 60 psi
Pressure tap M is the pump drive lubrication (left side engine enclosure removed to get to it)
it checked 45 psi at high idle, spec calls for 70 +- 10 psi
Transmission warmed up to 190-200.
I didn't take the reading on the converter outlet with the trans stalled as it says to, I did have it stalled heating it up and don't recall much pressure change.
Trans temp will go from 190-250 in 25 seconds, complete stall 3rd gear, full throttle. cools down to 210 in 48 seconds.
There is no hydraulic cooler.
It is not a differential steer.
When the trans gets hot running steady 3 or 4 hrs it is pretty slow to cool back down, and never really cools completely down.
Engine cooling system is pretty good, some wear on the sheeves. Belts tight, radiator clean, shrouds all there.
Last edited by zhkent; 08-12-2011 at 06:17 PM.
Make it look easy,
I'm no expert here but seems I've heard these symptoms before and "Bolt Thrower" was on it. Leaking torque converter or problem with scavenge pump. The check, if I remember right was to drain the TQ housing, then place a container under the drain.....start it up and see what volume comes out over time. Need some help with how much is acceptable.